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The role of citrate in plant-pathogen interactions
Bacterial plant pathogens have evolved a wide range of mechanisms to suppress the immune response that they trigger in their hosts, including the production of effectors and phytotoxins. The tri-carboxylic acid citrate, which is secreted into the apoplast by both bacterial pathogens and plant hosts...
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| Format: | Thesis |
| Language: | English |
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Department of Molecular and Cell Biology
2016
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| _version_ | 1867613173743353856 |
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| access_status_str | Open Access |
| author | Hendry, Tia Lynne |
| author2 | Ingle, Robert A |
| author_browse | Hendry, Tia Lynne Ingle, Robert A |
| author_facet | Ingle, Robert A Hendry, Tia Lynne |
| author_sort | Hendry, Tia Lynne |
| collection | Thesis |
| description | Bacterial plant pathogens have evolved a wide range of mechanisms to suppress the immune response that they trigger in their hosts, including the production of effectors and phytotoxins. The tri-carboxylic acid citrate, which is secreted into the apoplast by both bacterial pathogens and plant hosts has previously been shown to increase the virulence of the gram negative pathogen Pseudomonas syringae DC3000 (Pst DC3000), by acting both as a chemoattractant and as an inducer of genes associated with the type III secretion system (T3SS) and phytotoxin production. The effect of citrate on the host is less clear, though microarray analysis of Arabidopsis thaliana has demonstrated that application of exogenous citrate leads to the differential expression of 1876 genes suggesting that it might act as a metabolic signal for transcriptional reprogramming. In this study, functional enrichment analysis revealed statistically significant enrichment for gene ontology terms associated with defence in both citrate up-regulated and down-regulated gene sets. Furthermore this project demonstrated that exogenous citrate can increase the success of virulent Pst DC3000 infection in Arabidopsis; bacterial titres in plants pre-treated with citrate 24 hours prior to infection were significantly higher than those in control plants. This phenomenon was also observed in plants pre-treated with a non-metabolisable citrate analogue but not in plants pre-treated with another TCA cycle intermediate, malate, suggesting that it is citrate specific. However, it remains unclear whether the increased apoplastic citrate concentrations lead to increased bacterial titres through a suppressive effect on the host immune response, an enhanced induction of the T3SS system in Pst DC3000, or a combination of both. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/20529 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:31:56.645Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2016 |
| publishDateRange | 2016 |
| publishDateSort | 2016 |
| publisher | Department of Molecular and Cell Biology |
| publisherStr | Department of Molecular and Cell Biology |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/20529 The role of citrate in plant-pathogen interactions Hendry, Tia Lynne Ingle, Robert A Molecular and Cell Biology Bacterial plant pathogens have evolved a wide range of mechanisms to suppress the immune response that they trigger in their hosts, including the production of effectors and phytotoxins. The tri-carboxylic acid citrate, which is secreted into the apoplast by both bacterial pathogens and plant hosts has previously been shown to increase the virulence of the gram negative pathogen Pseudomonas syringae DC3000 (Pst DC3000), by acting both as a chemoattractant and as an inducer of genes associated with the type III secretion system (T3SS) and phytotoxin production. The effect of citrate on the host is less clear, though microarray analysis of Arabidopsis thaliana has demonstrated that application of exogenous citrate leads to the differential expression of 1876 genes suggesting that it might act as a metabolic signal for transcriptional reprogramming. In this study, functional enrichment analysis revealed statistically significant enrichment for gene ontology terms associated with defence in both citrate up-regulated and down-regulated gene sets. Furthermore this project demonstrated that exogenous citrate can increase the success of virulent Pst DC3000 infection in Arabidopsis; bacterial titres in plants pre-treated with citrate 24 hours prior to infection were significantly higher than those in control plants. This phenomenon was also observed in plants pre-treated with a non-metabolisable citrate analogue but not in plants pre-treated with another TCA cycle intermediate, malate, suggesting that it is citrate specific. However, it remains unclear whether the increased apoplastic citrate concentrations lead to increased bacterial titres through a suppressive effect on the host immune response, an enhanced induction of the T3SS system in Pst DC3000, or a combination of both. 2016-07-20T12:28:44Z 2016-07-20T12:28:44Z 2016 Master Thesis Masters MSc http://hdl.handle.net/11427/20529 eng application/pdf Department of Molecular and Cell Biology Faculty of Science University of Cape Town |
| spellingShingle | Molecular and Cell Biology Hendry, Tia Lynne The role of citrate in plant-pathogen interactions |
| thesis_degree_str | Master's |
| title | The role of citrate in plant-pathogen interactions |
| title_full | The role of citrate in plant-pathogen interactions |
| title_fullStr | The role of citrate in plant-pathogen interactions |
| title_full_unstemmed | The role of citrate in plant-pathogen interactions |
| title_short | The role of citrate in plant-pathogen interactions |
| title_sort | role of citrate in plant pathogen interactions |
| topic | Molecular and Cell Biology |
| url | http://hdl.handle.net/11427/20529 |
| work_keys_str_mv | AT hendrytialynne theroleofcitrateinplantpathogeninteractions AT hendrytialynne roleofcitrateinplantpathogeninteractions |